A vaccine to help prevent COVID-19
COVID-19 vaccine
A vaccine that helps the immune system protect against COVID-19, given through the national vaccination programme.
What is COVID-19 vaccine?
A COVID-19 vaccine helps your immune system recognise and defend against the coronavirus that causes COVID-19, lowering the chance of becoming seriously ill. It is a preventive measure, not a treatment for an existing infection. Different types exist, including mRNA, protein-based and viral-vector vaccines, all of which teach the body to respond to the virus without causing the illness. Most side effects are mild and short-lived, such as a sore arm or feeling fluey for a day or two. Serious allergic reactions are very rare, and a rare inflammation of the heart has been seen mainly in younger males after mRNA types. Which vaccine you are offered, and when, follows the national programme. This is general information; follow the advice of the national programme and your healthcare team.
Education and reference only. This is a plain-language guide to COVID-19 vaccine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
A COVID-19 vaccine is a preventive vaccine that helps the body build protection against COVID-19, the illness caused by the coronavirus, rather than treating an infection that has already taken hold. Several types are used: mRNA vaccines, which give the body instructions to make a harmless piece of the virus so the immune system learns to recognise it; protein-based vaccines, which contain a harmless piece of the virus directly; and viral-vector vaccines, which use a harmless carrier virus to deliver the instructions. All of them prepare the immune system without giving you COVID-19. In the UK, COVID-19 vaccines are offered through the national vaccination programme.
How it works
All COVID-19 vaccines work by showing the immune system a harmless part of the coronavirus, usually a piece of its surface 'spike', so the body learns to recognise it. mRNA vaccines deliver instructions for your own cells to make that harmless piece briefly; protein vaccines supply the piece directly; and viral-vector vaccines use a harmless carrier to deliver the instructions. In each case the immune system builds memory, so if you later meet the real virus your body can respond faster and more strongly. This reduces the chance of serious illness. Protection can fade over time and the virus changes, which is why booster doses are offered to certain groups.
Company & origin
Originated / developed by: Various manufacturers.
A vaccine offered in the UK through the national programme to help protect against COVID-19, the illness caused by the coronavirus.
Practical use
How to take COVID-19 vaccine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Have it as advised through the national vaccination programme; it is given as an injection, usually into the upper arm.
- Tell the staff about any previous serious allergic reaction, especially to a previous dose or its ingredients.
- You may be asked to wait a short while after the injection so staff can act if a rare allergic reaction occurs.
- Have any booster or further doses you are offered, as protection can fade over time.
- Seek medical advice if you get chest pain, breathlessness or a pounding heartbeat after an mRNA type.
Weighing it up
Advantages & disadvantages of COVID-19 vaccine
Advantages
- Lowers the chance of becoming seriously ill from COVID-19.
- Teaches the immune system to respond without giving you the illness.
- Offered free through the national programme to those who are eligible.
Disadvantages
- Commonly causes short-lived effects such as a sore arm and feeling fluey.
- Protection can fade over time and as the virus changes, so further doses may be needed.
- Very rarely a serious allergic reaction, or a rare heart inflammation mainly in younger males after mRNA types.
Practical use
Good to know
The key point is that a COVID-19 vaccine is preventive: it helps stop serious illness rather than treating an infection you already have. Most side effects are mild and short-lived, typically a sore arm where the injection is given and flu-like feelings such as tiredness, headache, aches or a mild fever for a day or two as the immune system responds. Two rarer safety points are worth knowing: a serious allergic reaction (anaphylaxis) can very rarely happen soon after the injection, which is why you may be asked to wait a short time afterwards and why staff are ready to treat it; and a rare inflammation of the heart or its lining (myocarditis or pericarditis) has been seen mainly in younger males after mRNA types, usually mild and settling, with chest pain, breathlessness or a pounding heartbeat being signs to seek medical advice. Which vaccine and how many doses you are offered depends on the national programme. This is general information; follow the national programme and your healthcare team's advice.
Who should not take it / use with caution
- People who have had a serious allergic reaction (anaphylaxis) to a previous dose or to an ingredient of that vaccine should not have the same one.
- If you are unwell with a high temperature, it may be sensible to wait until you feel better.
- Tell the team about any health conditions or weakened immune system, as advice on which vaccine and timing may differ.
Monitoring
- A short wait after the injection so staff can act if a rare allergic reaction occurs.
- Self-watching for chest pain, breathlessness or a pounding heartbeat after mRNA types.
- Reviewing eligibility for booster doses through the national programme over time.
Side effects
- A sore, red or swollen arm where the injection is given.
- Flu-like feelings such as tiredness, headache, aches, chills or a mild fever for a day or two.
- Very rarely a serious allergic reaction soon after, and rarely heart inflammation (myocarditis or pericarditis), mainly in younger males after mRNA types.
Key interactions
- It can usually be given alongside some other vaccines, but follow the advice of the team about timing.
- Tell the team if you take medicines that affect the immune system or blood thinners.
- There are no everyday food or drink interactions, but always mention your full medicines list.
Available as: An injection, usually given into the upper arm.
Answers
COVID-19 vaccine: frequently asked questions
What is the COVID-19 vaccine for?
It helps your immune system protect against COVID-19, the illness caused by the coronavirus, lowering the chance of becoming seriously ill. It is preventive, not a treatment.
What are the different types?
There are mRNA, protein-based and viral-vector vaccines; all teach the body to recognise a harmless part of the virus without giving you COVID-19.
What side effects are common?
Most are mild and short-lived, such as a sore arm and flu-like feelings like tiredness, headache or a mild fever for a day or two.
What are the rare risks?
A serious allergic reaction is very rare, and a rare heart inflammation has been seen mainly in younger males after mRNA types; seek advice for chest pain or breathlessness.
Which vaccine will I get?
Which vaccine and how many doses you are offered follows the national programme; this is general information, so follow the programme and your healthcare team's advice.
The wider class
About Vaccine (prevention of COVID-19)
COVID-19 vaccine belongs to the vaccine (prevention of covid-19) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF
- NICE CKS
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